Kidney stones affect 1 in 11 Americans at an annual cost of $10B, with both numbers steadily climbing. Watchful waiting is the preferred approach to stone management, but there are no means to predict when the stone will pass or if the stone will pass. Intervention is typically recommended once a stone is over 5 mm and usually involves breaking the stone into smaller fragments, which are then expected to pass on their own. Multiple studies have shown that these residual fragments often do not pass on their own and lead to symptomatic stone events in up to 50%, and secondary surgery in 20%, of the 700,000 procedures performed yearly. A non-invasive tool that could facilitate stone fragment passage would significantly improve the management of kidney stones. Technology: Ultrasonic propulsion is a non-invasive tool to move stones within the collecting space using acoustic radiation force. The technology uses an existing commercial diagnostic probe so the stone movement can be monitored in real-time with imaging. The technology has the potential to aid in the passage of small stones and fragments in an office setting, improve stone free rates immediately following lithotripsy procedures, and relieve pain by moving a stone blocking the ureter. Preliminary Data: Investigational results from a feasibility trial has shown the technology to be safe and effective in humans with stone repositioning in 14 of 15 subjects and an aggregate 30 stone fragments passed by 4 of 6 post-lithotripsy subjects. Specific Aims: This is a Fast Track proposal that will use Phase 1 to test technical advances from which final design specifications will be formed for commercial prototype development in Phase 2. Phase 1 Aim 1 expands the capabilities of our technology, augmenting the Push pulse designed to move one stone at a time in order to collectively move a cluster of small stone fragments. A custom phantom model will be used to quantify improvement in the Push efficiency of a broadened beam relative to that of the existing narrow-beam system. The outcome will improve an operator's ability to clear the many small residual fragments found in post-lithotripsy subjects in a short timeframe. Phase 2 includes integrating imaging that tracks an acoustic signature unique to stones and assembling a focus group all to improve the usability of the system, porting the technology onto an FDA-approved, OEM, complete, urological ultrasound system, and performing the safety and effectiveness tests necessary for application for an investigational device exemption. The outcome of this proposal will be a clinical trial-ready, commercially viable ultrasonic propulsion and imaging system that can effectively treat post-lithotripsy stone fragments.